1. Field of the Invention
The invention relates to a device for the cyclic rearrangement of a pile of rectangular or square sheets, or a so-called "picture-changer".
2. Description of the Related Art
Picture changers are known from U.S. Patent Specifications 4,238,898, 4,238,899, 4,241,528, 4,241,529, 4,245,417, 4,259,802 and 4,376,348. These specifications are all based on the principle that a pile of pictures, especially photographic prints, is held by two frame parts that are movable relative to one another, one of which may have a viewing window. During each complete cycle of movement of the frame parts, that is, pulling them fully away from each other and sliding them fully back together again, one picture is removed from one end of the pile and returned to the other end of the pile again. The picture changers have the following components for this:
A feeding means feeds pictures to a separating means; the separating means detaches an individual picture from the pile; a retaining means holds the individual picture separated from the pile in one of the frame parts whilst the remainder of the pile is held in the other frame part; a guide means guides the separated individual picture such that it goes onto the other end of the remainder of the pile.
The known picture-changers use one and the same element both as feeding means and also as retaining means for the individual picture, but owing to the different functions this is less advantageous than using a separate system for each of the functions mentioned.
The aim of the present invention is to provide a retaining means which is especially well adapted to the difficulties associated therewith. That is, where photographs are concerned, the edge of the sheet being separated (which comes free behind the separating means) may, on the one hand, be warped and bowed owing to the thin material and, on the other hand, due to the physical and chemical properties of the photographic papers, require especially strong separating forces.